System and method for patterning and depositing liquid metal film by using low-energy focused ion beam

Abstract

The invention provides a system and a method for patterning a solid-phase deposition liquid metal film by using a low-energy focused ion beam. The system comprises a liquid metal ion source, a deceleration electric field module, an ion beam pre-focusing module, an ion beam secondary focusing module, a deflection coil module, a sample table, a temperature control module and a positioning adjustment module. According to the system, the energy of the focused liquid metal ion beam is reduced through the deceleration electric field module, so that the liquid metal ion beam can directly realize patterned solid-phase deposition on the substrate, liquid metal ions are directly led out from the ion source, pollution is avoided, and the obtained film is high in purity and high in yield. And efficient preparation of the high-purity patterned liquid metal film can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid metal deposition, and in particular to a system and method for patterning and depositing a liquid metal film using a low-energy focused ion beam. Background Art

[0002] Liquid metal is a high-tech strategic emerging material that is liquid and flowable at room temperature and pressure and has high electrical and thermal conductivity. Liquid metal can be regarded as a mixture of positive ion fluid and free electron gas. Liquid metal can be used in the preparation of flexible circuits and devices. Patterned preparation of liquid metal film is the key to achieving high-quality preparation of flexible circuits and devices.

[0003] At present, the methods that can pattern the preparation of liquid metal films mainly include: thermal evaporation technology: This method can realize the patterning of liquid metal films by cooperating with photolithography technology, but the controllability of thermal evaporation technology is poor, the utilization rate of raw materials is low, and there are also problems such as contamination of the cavity and the inability to observe the deposition state in real time during deposition. Molecular beam epitaxy technology: This method can also realize the patterning of liquid metal films by cooperating with photolithography technology, but the deposition speed of the molecular beam epitaxial growth film method is slow, and there is also the problem that the deposition state cannot be observed in real time during deposition. Although these two processes can meet the needs of patterning the preparation of liquid metal films, both processes need to be used in conjunction with photolithography technology, and mask plates and photoresists are used in photolithography technology, which can easily cause damage to the surface of the deposited liquid metal, and the process steps are complex, the material consumption is large, and the manufacturing cost is high.

[0004] In order to simplify the preparation process and reduce the manufacturing cost, a dual-beam scanning electron microscope (SEM-FIB) is used to directly pattern and deposit liquid metal films. The method of depositing metal films by dual-beam scanning electron microscope is ion beam induced deposition, which uses the energy of the ion beam to excite chemical reactions to deposit metal films. Some metal organic gases (such as W(CO)6, WF6, Al(CH3)3, etc.) are sprayed on the area where deposition is required on the sample through a gas injection system. When the ion beam is focused on this area, the ion beam energy decomposes the organic matter, and the decomposed metal solid components are deposited and left on the solid surface to form a film layer, while the volatile organic components are pumped away by the vacuum system. Although the dual-beam scanning electron microscope can directly pattern and deposit liquid metal films, the induced gas used is not completely pumped away by the vacuum pump after decomposition, and there will still be residues in the film, resulting in poor film purity, and this deposition method is also prone to irradiation damage to the substrate surface. Therefore, how to simplify the process of patterning the preparation of liquid metal films and prepare high-quality patterned deposited liquid metal films is still a problem that needs to be solved in this field. Summary of the invention

[0005] The present invention provides a system for patterned deposition of liquid metal film by using a low-energy focused ion beam. The system reduces the energy of a focused liquid metal ion beam without significantly reducing the ion beam flow through a deceleration electric field module, changes the direction of the ion beam through a deflection coil, and enables direct patterned deposition of the liquid metal ion beam. Liquid metal ions are directly drawn out from an ion source without pollution, and the obtained film has high purity. The problem that the purity of liquid metal films prepared by direct patterned deposition using a dual-beam scanning electron microscope is poor and easy to cause damage to a substrate is solved, and efficient preparation of high-purity, patterned liquid metal films can be achieved.

[0006] To solve the above technical problems, the present invention provides a system for patterning and depositing a liquid metal film using a low-energy focused ion beam, comprising: a liquid metal ion source, used to emit a liquid metal ion beam; a deceleration electric field module, used to reduce the energy of the liquid metal ion beam; an ion beam pre-focusing module, used to pre-focus the liquid metal ion beam emitted by the liquid metal ion source; an ion beam secondary focusing module, used to re-focus the liquid metal ion beam after pre-focusing by the ion beam pre-focusing module; a deflection coil module, used to adjust the motion trajectory of the liquid metal ion beam after pre-focusing by the ion beam pre-focusing module; a sample stage, used to receive the low-energy focused liquid metal ion beam after energy reduction and focusing; a temperature control module, which is arranged at the lower end of the sample stage and is used to control the temperature of the sample stage; a positioning adjustment module, which is connected to the ion receiving stage and is used to adjust the lifting or tilting of the sample stage; the ion beam pre-focusing module, the deflection coil module, the ion beam secondary focusing module and the sample stage are arranged in sequence along the forward direction of the liquid metal ion beam.

[0007] In a preferred or optional embodiment, the deceleration electric field module is arranged between the ion beam secondary focusing module and the sample stage, the deceleration electric field module includes a deceleration lens and a deceleration power supply, the deceleration lens is arranged between the ion beam secondary focusing module and the sample stage, and the two ends of the deceleration power supply are electrically connected to the deceleration lens and the ion beam secondary focusing module respectively.

[0008] In a preferred or optional embodiment, the positive pole of the deceleration power supply is electrically connected to the deceleration lens, one end of the negative pole of the deceleration power supply is electrically connected to the ion beam secondary focusing module, and the other end of the negative pole of the deceleration power supply is grounded.

[0009] In a preferred or optional embodiment, the potential on the deceleration lens is the same as the potential on the sample stage, forming a field-free space between the deceleration lens and the sample stage.

[0010] The present invention also provides a method for patterning and depositing a liquid metal film using a low-energy focused ion beam, using the above system, comprising the following steps:

[0011] S100: applying an electric field to the liquid metal ion source to form a tip of the liquid metal, and then applying a negative electric field to pull the liquid metal at the tip to emit a liquid metal ion beam;

[0012] S200: After the liquid metal ion beam is pre-focused by the ion beam pre-focusing module, it enters the deflection coil module to adjust its position, then enters the ion beam secondary focusing module to focus and the deceleration electric field module to reduce its energy, and then emits a low-energy focused liquid metal ion beam;

[0013] S300: The low-energy focused liquid metal ion beam lands and is deposited on the sample stage. At the same time, the deflection coil module and the positioning adjustment module cooperate with each other to adjust the landing point of the low-energy focused liquid metal ion beam on the sample stage and form a set pattern on the sample stage. The temperature control module regulates the temperature of the liquid metal deposited on the sample stage so that the liquid metal deposited on the sample stage can grow in a controllable manner to obtain a patterned liquid metal film.

[0014] In a preferred or optional embodiment, a secondary electron detection system is provided between the deceleration electric field module and the sample stage, and the secondary electron detection system includes a secondary electron probe and further includes the following steps:

[0015] S400: The secondary electron detection system detects secondary electrons reflected from the sample stage and generates ion beam imaging to observe the deposition of low-energy focused liquid metal ion beams.

[0016] In a preferred or optional embodiment, a microscope is arranged between the deceleration electric field module and the sample stage, and the microscope includes an optical microscope.

[0017] In a preferred or optional embodiment, according to different components of the thin film to be deposited, the liquid metal added to the liquid metal ion source includes one or more of gallium, gallium-indium alloy, and gallium-indium-tin alloy.

[0018] In a preferred or optional embodiment, an EB mass analyzer module is provided between the ion beam pre-focusing module and the deflection coil module. The EB mass analyzer module can shield unnecessary ions when an alloy is used as an ion source.

[0019] In a preferred or optional embodiment, the energy of the low energy focused liquid metal ion beam upon landing is less than 100 eV.

[0020] In summary, the present invention has the following beneficial effects:

[0021] (1) The scheme of patterned deposition of liquid metal film of the present invention reduces the emission energy of the focused liquid metal ion beam by a deceleration electric field module, so that the liquid metal ions can be directly deposited. Moreover, due to the reduction of the energy of the focused liquid metal ion beam, the sputtering effect on the substrate surface is very weak, and basically no damage is caused to the substrate surface.

[0022] (2) In the scheme of patterned deposition of liquid metal film of the present invention, the deposited liquid metal film is derived from liquid metal ions drawn from a liquid metal ion source, and no pollution is generated in the entire preparation step. The prepared liquid metal film has extremely high purity;

[0023] (3) The solution of patterned deposition of liquid metal film of the present invention does not need to be used in conjunction with photolithography technology and does not require mask shielding. The deflection coil module and the positioning adjustment module cooperate with each other to adjust the landing point of the low-energy focused liquid metal ion beam on the sample stage, thereby realizing the design of liquid metal patterning.

[0024] (4) In the solution of patterned deposition of liquid metal film of the present invention, a temperature control module is further provided on the sample stage, and the solid-phase controllable growth of the liquid metal deposited on the sample stage is achieved by regulating the temperature of the sample stage.

[0025] (5) The scheme for patterned deposition of liquid metal film of the present invention also sets the deceleration electric field module between the ion beam secondary focusing module and the sample stage, which can avoid the sample from being exposed to the electric field, make the positioning of the ion beam more accurate, and monitor the deposition of liquid metal ions through secondary electrons during deposition. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic structural diagram of a system for patterned deposition of liquid metal film by low-energy focused ion beam in a specific embodiment of the present invention;

[0027] Figure 2 It is a structural schematic diagram of a deceleration electric field module in a specific implementation manner of the present invention; Description of the drawings:

[0029] 110-liquid metal ion source; 120-deceleration electric field module; 121-deceleration lens; 122-deceleration power supply; 130-ion beam pre-focusing module; 140-ion beam secondary focusing module; 150-deflection coil module; 160-E×B mass analyzer module; 210-sample stage; 220-temperature control module; 230-positioning adjustment module; 310-secondary electron probe; 320-microscope. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be noted that similar symbols and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not require further definition and explanation in the subsequent drawings.

[0033] The specific embodiment of the present invention provides a method for patterning and depositing a liquid metal film using a low-energy focused ion beam. The system mainly includes a transmitting system for generating and generating a low-energy focused ion beam, a receiving system for receiving the low-energy ion beam, and a secondary electron detection system for detecting the deposition condition. Figure 1 As shown, the transmitting system includes a liquid metal ion source 110, a deceleration electric field module 120, an ion beam pre-focusing module 130, an ion beam secondary focusing module 140, and a deflection coil module 150. The liquid metal ion source 110, the ion beam pre-focusing module 130, the deflection coil module 150, and the ion beam secondary focusing module 140 are arranged in sequence from top to bottom. The receiving system includes a sample stage 210, a temperature control module 220, and a positioning adjustment module 230. The deceleration electric field module 120 is disposed between the ion beam secondary focusing module 140 and the sample stage 210. The secondary electron detection system includes a secondary electron probe 310. The secondary electron detection system is disposed between the deceleration lens 121 and the sample stage 210. A microscope 320 is also disposed between the deceleration lens 121 and the sample stage 210. The microscope includes an optical microscope. Figure 2 As shown, the deceleration electric field module 120 includes a deceleration lens 121 and a deceleration power supply 122. The deceleration lens 121 is disposed between the ion beam secondary focusing module 140 and the sample stage 210. The positive electrode of the deceleration power supply 122 is electrically connected to the deceleration lens 121, one end of the negative electrode of the deceleration power supply 122 is electrically connected to the ion beam secondary focusing module 140, and the other end of the negative electrode of the deceleration power supply 122 is grounded, thereby controlling the potential on the deceleration lens 121 to be the same as the potential on the sample stage 210, and forming a field-free space between the deceleration lens 121 and the sample stage 210. A substrate is placed on the sample stage 210, and the substrate can be a silicon wafer or the like.

[0034] Focused ion beam technology (FIB) is a technology that uses an electric lens to focus an ion beam into a very small size to bombard the surface of a material to achieve material stripping and cutting. Since FIB technology is mainly used for cutting materials, the energy of the ion beam it emits is very high. When using FIB high-energy ion beams to directly pattern-assisted deposition to prepare metal films, the ion beams emitted by the FIB are very likely to damage the deposited substrate material, thereby affecting the preparation quality of the material. Therefore, in the present application, by setting a deceleration electric field between the ion beam secondary focusing module 140 and the sample stage 210, the emission energy can be reduced while ensuring the emission accuracy of the focused liquid metal ion beam, so that the focused liquid metal ion beam does not land on the substrate surface in a sputtering manner, but lands on the substrate surface in a deposition manner, so that not only will the substrate surface not be damaged, but the preparation of liquid metal film can also be achieved, that is, the solution of the present application can achieve the preparation of liquid metal film by direct patterned deposition using FIB. On the other hand, after the induced gas used in the dual-beam scanning electron microscopy method is decomposed, it is not completely pumped away by the vacuum pump, and there will still be residues in the film, resulting in poor film purity. In the solution of the present application, liquid metal ions are drawn from the liquid metal ion source 110, and no pollution will be generated in the entire preparation step, and the prepared liquid metal film has high purity. When the deceleration electric field is directly installed on the sample stage 210, the sample will be exposed to the electric field. When the sample surface is uneven, it will cause the deceleration electric field to be disordered and produce ion beam drift and shadow. On the other hand, since a positive potential is applied to the sample surface, it will also lead to the inability to obtain secondary electron imaging from the sample surface. Therefore, in the present application, the deceleration electric field module is arranged between the ion beam secondary focusing module and the sample stage, which can avoid the sample from being exposed to the electric field, make the positioning of the ion beam more accurate, and can also monitor the deposition of liquid metal ions through secondary electrons during deposition.

[0035] In a system with only an ion beam, without the imaging assistance of an electron beam, it is particularly difficult to observe the micron-scale patterns deposited on liquid metal. By designing a secondary electron detection system, preparing a secondary electron probe 310 and equipping a reflective objective microscope system, image observation can be achieved. The secondary electron probe 310 is mainly used for scanning ion beam imaging observation. It is installed on the lower side of the deceleration electric field module 120. The grid voltage is adjustable to capture more secondary electrons for imaging. Since the energy used for ion beam imaging is relatively high, secondary electron imaging can be used for samples that are resistant to radiation damage. For samples that are not resistant to radiation, this method cannot be used, so a pre-installed optical microscope is required for online observation.

[0036] The deflection coil module 150 mainly controls the movement of the liquid metal ion beam after pre-focusing treatment on the plane of the sample stage 210 through the deflection amplifier, so as to achieve local precise pattern drawing. The deflection coil module 150 is driven by piezoelectric ceramics and is a square hollow design as a whole. The positioning adjustment module 230 is installed at the lower end of the sample stage 210 and is driven by a traditional servo motor to control the working distance and tilt adjustment of the sample stage 210. The temperature control module 220 is installed at the lower end of the sample stage 210. Since the liquid metal ions need to achieve controllable growth after being deposited on the sample stage 210, liquid metal ion solid phase deposition is required, and solid phase deposition requires low temperature conditions. The temperature control module 220 mainly includes a cooling pipe carrying a coolant. The cooling pipe is distributed on the lower side of the sample stage 210 and contacts the table to exchange heat. The module uses nitrogen cooled by liquid nitrogen for cooling and nitrogen passed through an ice-water mixture for heating. The rough temperature control is achieved by adjusting the opening time of the solenoid valve within the sampling period and using the PID algorithm to accurately control the temperature.

[0037] The liquid metal added to the liquid metal ion source can be selected from one of the metals or alloys with low melting points such as gallium, gallium-indium alloy, gallium-indium-tin alloy, etc. In order to facilitate the coating of the alloy ion source, an E×B mass analyzer module can be set between the ion beam pre-focusing module and the deflection coil module. The E×B mass analyzer module separates the ions generated in the ion source according to the mass-to-charge ratio m / z and blocks the unnecessary ions, thereby achieving controllable and selective coating of the alloy ions. Gallium-based liquid metal has the characteristics of high fluidity, high thermal conductivity, low viscosity, safety and non-toxicity. It is an important component of the conductive unit and sensing unit in flexible electronic devices and is considered to be the core material for building stretchable electronic devices. However, as an emerging material, gallium-based liquid metal still faces many problems and challenges in the understanding and regulation of its basic physical properties. For example: (1) The melting point is not low enough (currently the lowest is -19°C), which leads to the failure of gallium-based liquid metal elastic electronic devices at low temperatures. Although it is generally believed that reducing the size is an effective way to reduce the melting point of the material, the influence of size on the melting point of liquid metal is still unclear. (2) Thin film patterning is difficult. Liquid metal has a strong metallic bonding effect, which leads to its large surface tension (about 10 times that of water), making it difficult to achieve thin film and patterning, which poses a challenge to device processing. (3) Micro-nano processing is challenging. With the high-end application, the characteristic size of liquid metal line width has also extended from hundreds of microns to microns and even nanometers. However, since liquid metal has multiple phases, complex solid-liquid or even liquid-liquid phase transitions will occur during the temperature change process. Traditional photolithography processes inevitably require multiple steps of heating and cooling, which makes it difficult to control the liquid metal phase after micro-processing. Although dual-beam scanning electron microscopes can use metal organic gases such as W(CO)6, WF6, Al(CH3)3 to directly pattern and deposit liquid metal films, there is currently no induction gas for liquid metal gallium deposition, which means that patterned gallium liquid metal films cannot be prepared using dual-beam scanning electron microscopes. Liquid metal gallium can be used as an ion source for FIB, so the method of this application can be used to prepare patterned gallium liquid metal films.

[0038] This embodiment provides a method for preparing a liquid metal film by patterned deposition using gallium as a liquid metal ion source, and the specific steps are as follows:

[0039] S100: applying an electric field to the liquid metal gallium ion source to form a tip of the liquid metal, and then applying a negative electric field to pull the liquid metal at the tip to emit a liquid metal gallium ion beam;

[0040] S200: After the liquid metal gallium ion beam is pre-focused by the ion beam pre-focusing module 130, it enters the deflection coil module 150 to adjust its position, then enters the ion beam secondary focusing module 140 to focus, and then enters the deceleration electric field module 120 to reduce its energy, and then the emitted beam current density is 109 A / (cm 2 sr) low-energy focused liquid metal gallium ion beam;

[0041] S300: The low-energy focused liquid metal gallium ion beam lands with an energy of less than 100 eV and is deposited on the sample stage 210. At the same time, the deflection coil module 150 and the positioning adjustment module 230 cooperate with each other to adjust the landing point of the low-energy focused liquid metal gallium ion beam on the sample stage 210, and form a set pattern on the sample stage 210. The temperature control module 220 controls the temperature of the liquid metal gallium deposited on the sample stage 210, so that the liquid metal gallium ions deposited on the sample stage 210 can grow in a controllable manner, and a patterned liquid metal gallium film is obtained;

[0042] S400: The secondary electron detection system detects the secondary electrons reflected from the sample stage 210 and forms an image to observe the deposition of the low-energy focused liquid metal ion beam.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for patterning and depositing a liquid metal film using a low-energy focused ion beam, characterized in that: include: A liquid metal ion source (110) for emitting a liquid metal ion beam; A deceleration electric field module (120), used for reducing the energy of the liquid metal ion beam; An ion beam pre-focusing module (130) for pre-focusing the liquid metal ion beam emitted by the liquid metal ion source (110); An ion beam secondary focusing module (140) for refocusing the liquid metal ion beam pre-focused by the ion beam pre-focusing module (130); A deflection coil module (150) for adjusting the motion trajectory of the liquid metal ion beam after being pre-focused by the ion beam pre-focusing module (130); A sample stage (210) is used to receive the low-energy focused liquid metal ion beam after energy reduction and focusing; A temperature control module (220), the temperature control module (220) being arranged at the lower end of the sample stage (210) and being used for regulating the temperature of the sample stage (210); A positioning adjustment module (230), the positioning adjustment module (230) being connected to the ion receiving platform (210) and used for adjusting the lifting or tilting of the sample platform (210); The ion beam pre-focusing module (130), the deflection coil module (150), the ion beam secondary focusing module (140) and the sample stage (210) are arranged in sequence along the advancing direction of the liquid metal ion beam.

2. The system according to claim 1, characterized in that The deceleration electric field module (120) is arranged between the ion beam secondary focusing module (140) and the sample stage (210), and the deceleration electric field module (120) comprises a deceleration lens (121) and a deceleration power supply (122). The deceleration lens (121) is arranged between the ion beam secondary focusing module (140) and the sample stage (210), and two ends of the deceleration power supply (122) are electrically connected to the deceleration lens (121) and the ion beam secondary focusing module (140), respectively.

3. The system according to claim 2, characterized in that The positive pole of the deceleration power supply (122) is electrically connected to the deceleration lens (121), one end of the negative pole of the deceleration power supply (122) is electrically connected to the ion beam secondary focusing module (140), and the other end of the negative pole of the deceleration power supply (122) is grounded.

4. The system according to claim 2, characterized in that The potential on the deceleration lens (121) is the same as the potential on the sample stage (210), and a field-free space is formed between the deceleration lens (121) and the sample stage (210).

5. A method for patterning and depositing a liquid metal film using a low-energy focused ion beam, characterized in that: Using the system according to any one of claims 1 to 4, comprising the following steps: S100: applying an electric field to the liquid metal ion source (110) to form a tip of the liquid metal, and then applying a negative electric field to pull the liquid metal at the tip to emit a liquid metal ion beam; S200: After the liquid metal ion beam is pre-focused by the ion beam pre-focusing module (130), it enters the deflection coil module (150) to adjust its position, then enters the ion beam secondary focusing module (140) to focus and the deceleration electric field module (120) to reduce its energy, and then emits a low-energy focused liquid metal ion beam; S300: The low-energy focused liquid metal ion beam lands and is deposited on the sample stage (210), and at the same time, the deflection coil module (150) and the positioning adjustment module (230) cooperate with each other to adjust the landing point of the low-energy focused liquid metal ion beam on the sample stage (210), and form a set pattern on the sample stage (210), and the temperature control module (220) regulates the temperature of the liquid metal deposited on the sample stage (210), so that the liquid metal deposited on the sample stage (210) can grow in a controllable manner, thereby obtaining a patterned liquid metal film.

6. The method according to claim 5, characterized in that A secondary electron detection system is provided between the deceleration electric field module (120) and the sample stage (210), wherein the secondary electron detection system comprises a secondary electron probe (310) and further comprises the following steps: S400: The secondary electron detection system detects secondary electrons reflected from the sample stage (210) and generates ion beam imaging to observe the deposition of the low-energy focused liquid metal ion beam.

7. The method according to claim 5, characterized in that A microscope (320) is arranged between the deceleration electric field module (120) and the sample stage (210), and the microscope (320) comprises an optical microscope.

8. The method according to claim 5, characterized in that The liquid metal added to the liquid metal ion source (110) includes one or more of gallium, gallium-indium alloy, and gallium-indium-tin alloy.

9. The method according to claim 6, characterized in that An EB mass analyzer module (160) is arranged between the ion beam pre-focusing module (130) and the deflection coil module (150).

10. The method according to claim 5, characterized in that The energy of the low-energy focused liquid metal ion beam when landing is less than 100 eV.

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